Gas turbine engines are becoming more widely used, for example, in fire-fighting and other equipment where the public may be in physical proximity to the engine. Accordingly, the public liability factor has focused increased attention on the rare catastrophic failures of turbine engines, usually resulting from overheating, and on over-temperature protective circuits to prevent such accidents.
The manufacturers of gas turbine engines have determined the maximum time periods that the engines can withstand over-temperatures at certain specified temperature levels. Over-temperature control circuits which have been proposed heretofore, have included derivative temperature monitoring circuits which utilized thermocouple signals. These circuits involved charge derived signals and were very susceptible to electromagnetic interference (EMI). Accordingly, they were not well suited to engine environments.
It is therefore a principal object of the invention to provide a simple and more reliable turbine over-temperature protection circuit, and one which is compatible with present-day technology.